Image forming apparatus

Abstract

To provide a technique that enables skew detection of a sheet by a simple constitution.SOLUTION: An image formation device includes: a transport path where a sheet is transported; a member that abuts a center part in a width direction that intersects with a transport direction; first timing detection means that detects first timing when the sheet passes through a first position on the transport path; an abutting member that has a first abutting part that abuts the sheet passing through a second position that is more downstream in the sheet transport direction on the transport path than the first position and can contact at least one end side in the sheet width direction and a second abutting part that can contact the other end side in the sheet width direction, and moves from a non-detection position to a detection position by abutting of the sheet on either the first abutting part or the second abutting part; second timing detection means that detects timing when the abutting member has moved to the detection position; and skew detection means that detects the skew of the sheet based on respective time differences.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sheet feeding device, an image forming apparatus, and a skew detection system.

Background Art

[0002] Conventional sheet feeding devices include a transport mechanism for transporting sheets placed on a placement tray, and are configured to be able to detect skew of the transported sheets using a plurality of sensors in the width direction orthogonal to the transport direction (Patent Document 1). Also, there is a configuration having two skew detection means for one sheet width direction, and when these are taken as one set, two or more sets, that is, having four or more skew detection means (Patent Document 2). However, in the configuration of the detection means described in Patent Document 1, the size of the sheet for which skew can be detected is limited. Further, in the detection configuration described in Patent Document 2, the number of detection means must be increased in order to widen the range of sheet size correspondence.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a technique capable of accurately detecting skew of a sheet with a low-cost and simple configuration in which the number of detection sensors can be reduced, by acquiring detection information between sensors.

Means for Solving the Problems

[0005] To achieve the above object, an image forming apparatus of the present invention includes a transport path for transporting sheets, Regarding the width direction intersecting the sheet conveyance direction , of the sheet Contact the central portion including a first moving part that moves , The first moving part When the sheet passes through the first position in the conveyance path moves when, and the first moving part has moved First timing detection means for detecting the first timing, A contact portion that contacts the sheet passing through the second position downstream of the sheet in the conveyance direction in the conveyance path from the first position, and has at least a first contact portion that can contact one end side in the width direction of the sheet and a second contact portion that can contact the other end side in the width direction of the sheet, and is configured to move from a non-detection position to a detection position when the sheet contacts at least one of the first contact portion and the second contact portion a second moving part and, the a second moving part Second timing detection means for detecting the second timing when it moves to the detection position, Skew detection means for detecting the skew of the sheet based on the time difference between the first timing and the second timing, characterized by comprising. To achieve the above object, the image forming apparatus of the present invention A conveyance path for conveying a sheet, Regarding the width direction intersecting the sheet conveyance direction , of the sheet Contact the central portion including a first moving part that moves The first moving part , moves when, and the first moving part has moved When the sheet passes through the first position in the conveyance path a second moving part First timing detection means for detecting the first timing, A contact portion that contacts the sheet passing through the second position downstream of the sheet in the conveyance direction in the conveyance path from the first position, and has a first contact portion that can contact one end side in the width direction of the sheet and a second contact portion that can contact the other end side in the width direction of the sheet, and is configured to move from a non-detection position to a detection position when the sheet contacts both the first contact portion and the second contact portion a second moving part and, the

Figure 1

Advantages of the Invention

[0006] According to the present invention, the number of detection sensors is small, the configuration is low-cost and simple, detection information between sensors can be acquired, and skew of the sheet can be detected accurately.

Brief Description of the Drawings

[0007]

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Best Mode for Carrying Out the Invention

[0008] <Example 1> Hereinafter, an image forming apparatus equipped with a sheet feeding device according to the present invention will be described. The mode for carrying out this invention will be exemplified and described in detail based on examples. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in these examples should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions, and the scope of this invention is not intended to be limited to the following embodiments.

[0009] Here, an electrophotographic color laser printer (hereinafter referred to as LBP) as an image forming apparatus will be described with reference to the drawings as an example. Although the sheet feeding device of the embodiment of the present invention is applied to the LBP, the present invention is not limited thereto, and it may be applied to a copying machine, an inkjet printer, or the like.

[0010] First, the schematic configuration of the LBP 100 as an image forming apparatus will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view of the LBP 100 according to an embodiment of the present invention. In the conveyance path until an image is formed on the sheet S and conveyed to the discharge unit 113, first, the image forming unit 100A will be described. The image forming unit 100A is provided in the LBP apparatus main body 100 and is an image forming unit that forms an image by an electrophotographic method. This image forming unit 100A includes four photosensitive drums 101Y, 101M, 101C, and 101K that form toner images of four colors: yellow, magenta, cyan, and black. An endless intermediate transfer belt that contacts these four photosensitive drums and to which the toner images formed on the four photosensitive drums 101Y, 101M, 101C, and 101K are primarily transferred Transfer roller 102. A nip is formed from the inner peripheral side of the intermediate transfer belt 102 with respect to the photoreceptor drums 101Y, 101M, 101C, and 101K, and a potential difference is generated between the photoreceptor drums 101Y, 101M, 101C, and 101K and the intermediate transfer belt 102 to perform primary transfer of the toner image. Further, it is composed of primary transfer rollers 106Y, 106M, 106C, 106K and a secondary transfer roller 105 that forms a nip with the outer peripheral side of the intermediate transfer belt 102 and performs secondary transfer of the image transferred to the intermediate transfer belt 102 onto the sheet S.

[0011] When the image forming operation is started in the image forming unit 100A, light corresponding to the image signal is irradiated onto the photoreceptor drums 101Y, 101M, 101C, 101K charged to a certain potential by the laser scanner 103. Then, an electrostatic latent image is formed on the photoreceptor drums 101Y, 101M, 101C, 101K. Next, by developing with the toner stored in the developing cartridges 104Y, 104M, 104C, 104K, a toner image (visible image) is formed on the photoreceptor drums 101Y, 101M, 101C, 101K. The toner images formed on the photoreceptor drums 101Y, 101M, 101C, 101K are then primarily transferred to the intermediate transfer belt 102, and the toner images riding on the intermediate transfer belt 102 are conveyed by the intermediate transfer belt 102 to the secondary transfer section.

[0012] In parallel with such toner image forming operations, sheets S are fed one by one from the sheet feeding device 20. The sheet S is conveyed to the secondary transfer unit formed by the nip between the intermediate transfer belt 102 and the secondary transfer roller 105 by the registration roller 30. Here, since it is necessary to align the position of the sheet S in the sheet conveyance direction with respect to the toner image formed on the intermediate transfer belt 102, the timing of the sheet S is adjusted by controlling the conveyance speed of the registration roller 30. Then, by applying a bias to the secondary transfer roller 105 in the secondary transfer unit, the toner image is transferred from the intermediate transfer belt 102 to the sheet S. The sheet S onto which the toner image has been transferred is then conveyed to the fixing means 111, and the toner image is fixed to the sheet S by being heated and pressed in the fixing means 111. After fixing, the sheet S is discharged to the discharge unit 113 at the upper part of the apparatus by the discharge roller 112.

[0013] Here, the sheet conveyance unit in this embodiment will be described in detail with reference to FIGS. 2, 3, 4A, and 4B. FIG. 2 is a schematic cross-sectional view of the sheet conveyance unit according to the first embodiment, FIG. 3 is a schematic perspective view of the registration shutter 32 unit according to the first embodiment, FIG. 4A is an operation diagram when the sheet S abuts on the sheet conveyance unit according to the first embodiment, and FIG. 4B is an operation diagram when the sheet S passes through the sheet conveyance unit according to the first embodiment.

[0014] FIG. 2 shows a registration roller 31, a registration shutter 32, a registration shutter holder 33, a registration sensor detection unit 34, and a registration sheet metal 35 facing the registration roller 30. Further, a conveyance roller 39, a conveyance roller 40 facing the conveyance roller 39, a conveyance sensor 41, and a conveyance sensor detection unit 42 are arranged upstream of the arrangement of these components.

[0015] FIG. 4A(a) is a cross-sectional view of the vicinity of the registration shutter 32 immediately before the large-slanted sheet contacts the registration shutter 32, and FIG. 4A(b) is a perspective view of the vicinity of the registration shutter 32 immediately before the large-slanted sheet contacts the registration shutter 32. Further, FIG. 4B(a) is a cross-sectional view of the vicinity of the registration shutter 32 immediately after the large-slanted sheet contacts and passes through the registration shutter 32, and FIG. 4B(b) is a perspective view of the vicinity of the registration shutter 32 immediately after the large-slanted sheet contacts and passes through the registration shutter 32. Note that, for FIGS. 4A and 4B, some of the components shown in FIG. 2 are not shown in order to explain the operation more clearly.

[0016] First, the schematic configuration of the sheet conveyance unit will be described with reference to FIG. 2. As shown in FIG. 2, the sheet fed from the sheet feeding device is guided to the nip formed by the conveyance roller 39 and the conveyance roller 40, and passes through the conveyance roller 40 disposed in the vicinity of the nip. Thereafter, it is conveyed to the registration shutter 32 through the conveyance path formed by the upper conveyance guide 38 and the lower conveyance guide 37. When the sheet has a slight skew, the skew is corrected by the registration shutter 32, and it is guided to the nip formed by the registration roller 30 and the registration roller 31, and is conveyed to the downstream image forming unit 100A and the fixing means 111. Note that the nip portion formed by the registration roller 30 and the registration roller 31 and the registration shutter 32 are disposed at positions quite close to the sheet conveyance direction.

[0017] Next, the configuration around the registration shutter 32 will be described with reference to FIG. 3. The registration shutter 32 is engaged with a registration shutter holder 33 and is configured to be rotatable relative to the registration shutter holder 33 about a rotation center A. The registration shutter holder 33 is attached to a registration sheet metal 35 and is biased by a registration biasing member 36, and the three components of the registration shutter 32, the registration shutter holder 33, and the registration sheet metal 35 are configured to be rotatable about a rotation center B. Further, the registration shutter holder 33 has a downstream sensor light-shielding portion X. In a non-detection position where the registration shutter 32 is not rotating, the downstream sensor light-shielding portion X does not block the registration sensor detection portion 34. Then, when the conveyed sheet passes through and the registration shutter 32 rotates (moves), the rotation state of the registration shutter 32 is detected by the downstream sensor light-shielding portion X blocking the registration sensor detection portion 34. Note that the position where the registration shutter 32 has rotated is defined as a detection position.

[0018] The operations of the conveyance roller 40 and the registration sensor when a more obliquely oriented sheet is conveyed will be described with reference to FIGS. 2, 4A, and 4B. Here, it is assumed that no conveyance acceleration / deceleration control of the sheet is performed between the sheet conveyance sections, that is, between the conveyance roller 39 and the registration roller 30. First, as shown in FIG. 2, the conveyance roller 40 provided at the first position in the sheet conveyance path is disposed substantially at the center (central portion) in the width direction intersecting the sheet conveyance direction. Here, as the first timing detection means, a conveyance sensor detection unit 42 including the conveyance roller 40, the upstream sensor light-shielding portion Y, and the conveyance sensor 41 is configured. The upstream sensor light-shielding portion Y is a flag member that contacts and moves along the sheet. The upstream sensor light-shielding portion Y rotates when the central portion in the width direction of the sheet passes through the first position in the conveyance path (first timing), and switches the transmission and light-shielding states of the conveyance sensor 41. Note that the upstream sensor light-shielding portion Y is disposed substantially at the center in the sheet width direction. Therefore, the timing at which the upstream sensor light-shielding portion Y rotates to shield the conveyance sensor 41 is the same whether an obliquely oriented sheet or a non-obliquely oriented sheet is conveyed. Therefore, it is possible to detect the obliquely oriented state of the sheet based on the time difference from the second detection timing at which the detection timing varies depending on the obliquely oriented state of the sheet described later.

[0019] Next, the operations of the second timing detection means are shown in FIGS. 4A and 4B. Here, as the second timing detection means, a registration sensor detection unit 34 including a registration sensor, a registration shutter 32, a registration shutter holder 33, and a downstream sensor light-shielding portion X (for second timing detection), a registration sheet metal 35, and a registration biasing member 36 are configured. The second timing detection means is provided at a second position downstream in the conveyance direction from a first position where the conveyance roller 40 is located. The registration shutter 32 has a first contact portion against which one end side in the width direction of the conveyed sheet S abuts, and a second contact portion that can contact the other end side, and is a contact member that abuts against the sheet S. Further, the first contact portion is provided so as to be able to contact a region closer to one end than the central portion in the width direction of the sheet, and the second contact portion is provided so as to be able to contact a region closer to the other end than the central portion in the width direction of the sheet. Furthermore, when the contact portion abuts against the conveyed sheet, the registration shutter 32 rotates, and the downstream sensor light-shielding portion X detects the second timing at which the registration shutter 32 moves from the non-detection position to the detection position (second timing detection means).

[0020] The operation timing of the registration sensor is mainly divided into two operations depending on the skew amount of the conveyed sheet. The first timing is a timing that is not significantly different from that of a non-skewed sheet. For a skew amount that can be corrected by the registration shutter 32 caused by conveyance variations, first, the leading edge of the sheet that precedes in the conveyance direction abuts against the registration shutter 32 and forms a loop in the conveyance path. Then, the leading edge of the sheet on the delayed side abuts against the registration shutter 32, and only after the leading edges of the sheet are aligned does the registration shutter 32 retract and rotate from the conveyed sheet, enabling the conveyance of the sheet to the downstream registration roller 30. Therefore, in the case of a skew amount that can be corrected by the registration shutter 32, the operation timing is not significantly different from that of a non-skewed sheet.

[0021] The second timing is the timing at which the registration sensor operates earlier compared to the non-skewed sheet. This occurs because for a large amount of skew (major skew) that cannot be corrected by the registration shutter 32, the leading edge of the leading sheet S is conveyed around the contact portion of the registration shutter 32 with almost no loop formation. First, when a sheet S with the rear side leading significantly in the sheet width direction is conveyed, the state shown in FIG. 4A is reached at the moment when the leading edge of the leading rear side of the sheet contacts the registration shutter 32. In the case of a correctable amount of skew, the rear side of the leading sheet forms a loop by the registration shutter 32, and the sheet S is blocked by the biasing force of the registration biasing member 36 until the leading end portion of the sheet on the front side of the sheet contacts the registration shutter 32. However, as shown in FIG. 4A, when the skew is large, the loop formation amount inevitably becomes large. Then, in the loop formation space within the conveyance path formed by the upper conveyance guide 38 and the lower conveyance guide 37, before the leading end portion of the sheet on the front side of the sheet contacts the registration shutter 32, the loop amount that must be formed on the rear side is not formed. The reason is that the sheet S looped on the rear side immediately hits the upper conveyance guide 38, and due to the reaction force of the sheet S, the registration shutter 32 is immediately rotated. As a result, the registration shutter 32 can hardly correct the skew, and its operation timing also becomes earlier compared to a non-skewed sheet.

[0022] Therefore, the timing for detecting the second timing is different between the sheet that has obliquely advanced and the sheet that has not obliquely advanced. For this reason, if the time difference in the detection timing between the conveyance sensor detection unit 42 that detects the first timing and the registration sensor detection unit 34 that detects the second timing is compared for the sheet that has not obliquely advanced and the sheet that has obliquely advanced, it is possible to detect the oblique advance. As described above, the first timing detects the timing when the conveyance roller 40 rotates. However, since the position of the conveyance roller 40 is arranged substantially at the center (central portion) in the sheet width direction, the detection timing is the same for the sheet that has obliquely advanced and the sheet that has not obliquely advanced. That is, in the sheet width direction, the location where passage is detected by the first timing detection means is different from the location where contact is detected by the second timing detection means, and is also the location where the detection timing is the same for the sheet that has obliquely advanced and the sheet that has not obliquely advanced. Note that as the oblique advance detection means, it is also possible to calculate approximately the amount of oblique advance. In this embodiment, the value of the time difference is smaller for the sheet that has obliquely advanced compared to the sheet that has not obliquely advanced.

[0023] One of the factors causing the sheet to obliquely advance greatly is that there is a setting error in which the side regulation 24 that regulates the sheet width direction of the sheet conveyed in the cassette 23 (sheet storage unit) that stores a plurality of sheets is set in a state where it extends wider than the size of the conveyed sheet width. The purpose of this embodiment is to notify this. However, with the oblique advance detection method described above, if only one large oblique advance is detected and it is determined that it is due to a setting error, for example, there may be a case where the user has made a setting error only for the top sheet when setting the sheet in the cassette 23, so there is a risk of false notification. Therefore, in order to notify with a certain confidence level without false notification, it is necessary to perform arithmetic processing on the detected oblique advance in a certain aggregated unit according to a specific algorithm.

[0024] The algorithm for this arithmetic processing will be described with reference to FIG. 9. FIG. 9 shows the side regulation setting It is a flowchart showing the main process until Tomis is notified. Here, the value of the time difference between the first timing by the conveyance sensor detection unit 42 and the second timing by the registration sensor detection unit 34 is defined as the T value. As described above, the T value when the sheet is greatly skewed is smaller than the T value when it is not skewed. First, the T value is reset using the cassette 23 opening / closing as a trigger, and when the paper feed starts, the T values are acquired one by one and accumulated (acquire multiple time difference values). Then, according to the principle described above, the T value of the sheet that is least skewed, that is, the sheet that is conveyed most straight, theoretically becomes the MAX value. Therefore, the MAX value of the T value at the end of the JOB is calculated as the reference data (comparison value). After that, the difference between the T_MAX value and the T values other than the T_MAX value is calculated for a predetermined number of sheets, for example, 100 sheets, and the sum of each 100 sheets is defined as the index value (integrated value of the difference). This index value is a value indicating the degree of skewness of the sheets stored in the sheet storage unit, and when it exceeds a certain predetermined threshold, it is determined that there may be a side regulation setting error.

[0025] If the paper has not been fed for a predetermined number of sheets (for example, 100 sheets or more) and the opening / closing of the cassette 23 is detected, the number of data for calculating the index value is small and the confidence level of the determination becomes low. Therefore, the side regulation setting error determination is not performed, UNKNOWN is notified, and the T values and T_MAX value for the number of sheets not yet reached are reset. Also, even if the paper has not been fed for 100 sheets or more, if the opening / closing of the cassette 23 is not detected, and it is detected by the sheet type discrimination means (not shown) that the sheet type does not change, and the predetermined number of sheets is reached by subsequent paper feeding, the index value is calculated and the side regulation setting error determination is performed. Note that the value of the predetermined number of sheets, for example, 100 sheets, mentioned here does not necessarily have to be this number and can be arbitrarily set according to the detection accuracy. After that, based on the side regulation setting error determination result, trouble shooting, etc. are notified. Above, the formula for the index value described above in the case of a predetermined number of 100 sheets is as follows. TIFF0007693340000001.tif34170 Here, those with a difference in T value of 1 or less are due to the influence of conveyance variations. In order to increase the determination accuracy of side regulation set errors, the difference in T value may be squared to reduce its contribution. The index value in that case is given by the following formula. TIFF0007693340000002.tif34170 Note that by using the index value based on the difference in T value, there is an advantage that the influence of skew caused by factors such as each conveyance roller alignment until reaching the conveyance sensor detection unit 42 can be canceled out computationally. Also, when the conveyance roller 39 wears due to progress of durability, the diameter of the conveyance roller 39 becomes smaller, so the T value becomes longer. However, by using the index value based on the difference in T value, there is also an advantage that it is not necessary to change the threshold value according to the degree of durability progress and it can be set fixedly. Also, although the T value changes depending on the paper type, since the difference is taken for the predetermined threshold value there is also an advantage that it is not necessary to change it and it can be set fixedly.

[0026] Furthermore, since the index value obtained by the above method is different from the standard deviation and variance value which are values indicating variation, for example, even when the user sets the sheet bundle in the cassette 23 with the sheet bundle tilted uniformly in one direction in the side regulation set error state, the set error can be accurately notified. In this case, if the standard deviation or variance value is used as the index value, the sheet skews, but the skew amount is almost constant and does not vary. Therefore, when the standard deviation or variance value is used as the index value, the side regulation set error cannot be correctly notified.

[0027] As described above, by calculating the T value and using it as the index value (integrated value of the difference), it is possible to surely determine a side regulation set error within the LBP apparatus main body 100 and provide highly reliable troubleshooting. Since the registration shutter 32 unit needs to be configured to accurately detect the registration sensor in order to match the transfer timing in the secondary transfer unit as described above, for example, measures are taken such that the sheet does not flutter within the transport path of the registration shutter 32 unit. Therefore, by using the registration sensor detection unit 34 as one means for calculating the T value, it is possible to obtain a T value with higher accuracy than when using a normal transport sensor detection unit, and it is also possible to improve the detection accuracy of skew.

[0028] In this embodiment, the T value is calculated at the detection timing of the leading end of the sheet, but the T value may also be calculated at the detection timing of the trailing end of the sheet. Further, the distance between the transport sensor detection unit 42 and the registration sensor detection unit 34 may be calculated from the rotation speed of a transport motor (not shown) that rotates the transport roller 39, and this value may be treated in the same manner as the T value.

[0029] As a comparative example, the content of Patent Document 1 is shown. Patent Document 1 mainly includes a sheet detection sensor, a sheet detection sensor, a sheet detection sensor, and a paper feed tray. The position of the sheet detection sensor is arranged at the center in the sheet width direction. Depending on whether the width of the stacked sheets is specified to be uniform or not, at least two detection means are selected from a plurality of positions, and an abnormal state such as skew of the transported sheet is determined based on the difference in the detection timing of the sheet by the selected detection means. However, when different sizes are mixed and small-sized sheets are mixed, the small-sized sheets may not be transported to the position of the sheet detection sensor. In this case, skew cannot be correctly detected using the sheet detection sensor and the sheet detection sensor. Therefore, approximately the amount of skew is calculated based on the elapsed time of these sensors using one of the sensors (in this case, the sheet detection sensor) provided at a plurality of positions in the width direction and the sheet detection sensor.

[0030] However, in Patent Document 1, regardless of whether the sheet passed by the user is small-sized or large-sized, a plurality of detection means must be provided at one detection position, which increases the cost accordingly. Further, a means for determining whether small-sized sheets are mixed and determining which sheet detection sensor to use at one detection position is required, which also increases the cost accordingly.

[0031] Also, in Patent Document 2, at least two or more sets of diagonal detection means composed of detection units are provided in a paired manner centered on the central portion in the width direction of the original document in the main scanning direction. Each set includes one that can only detect a narrow original document and one that can detect both narrow and wide original documents, and they are selectively used for detection according to the width size of the original document. The reason for selectively using according to the width size of the original document is to accurately detect the diagonal. In this way, by making the distance in the width direction between the two sensors as long as possible with respect to the width of the sheet being passed, the diagonal is accurately detected.

[0032] However, if the sensor interval in the original document width direction is increased to improve the detection accuracy of the diagonal, small-sized original documents cannot be detected. Therefore, it is necessary to have at least two or more sets of diagonal detection means, which increases the cost accordingly. Necessarily, the cost increases accordingly.

[0033] In this embodiment, compared with the diagonal detection means of the prior documents 1 and 2, the number of detection sensors is reduced, and with a low-cost and simple configuration, by acquiring the detection information between the sensors, a configuration is achieved in which the diagonal of the sheet can be accurately detected.

[0034] The control block of this embodiment will be described with reference to FIG. 11. Here, only the parts related to this embodiment are extracted and described. Inside the image forming apparatus 500, the signal of the first timing detection means 511 in the sheet conveyance path 510 and the second timing detection means 513 by the contact member 512 are input to the skew detection unit 515. These signals are input to the arithmetic processing unit 514 in the skew detection unit 515, and the above-described arithmetic processing is performed. Then, when the skew of the sheet is detected based on the result of the arithmetic processing, a signal is input to the notification unit 530. Further, the control unit 520 includes a CPU 521 that controls various operations, a RAM 522 that temporarily stores control data, and a ROM 523 that stores a program and a control table necessary for operations in a non-volatile manner, and is configured to control the image forming apparatus 500.

[0035] <Example 2> Example 2 will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic cross-sectional view of the sheet conveyance unit according to Example 2, and FIG. 6 is a schematic perspective view of the paper width sensor 52 unit according to Example 2. Regarding the parts overlapping with the description of the above-described embodiment, the same reference numerals are given and the description is omitted. As shown in FIGS. 5 and 6, in this embodiment, a paper width sensor detection unit 53 is used instead of the registration sensor detection unit 34 used for T value calculation in Example 1.

[0036] In FIG. 5, the configuration of the conveyance sensor detection unit 42 upstream of the paper width sensor detection unit 53 is the same as that in the first embodiment, so it is omitted. As shown in FIGS. 5 and 6, the paper width sensor 52 has two contact portions that contact the sheet, a rear paper width sensor contact portion 52R, a front paper width sensor contact portion 52F, and a downstream sensor light-shielding portion X at one location. And it is urged by the paper width sensor biasing member 54 and is supported so as to be rotatable about the rotation center C. Here, for example, even if a sheet that is obliquely advancing with the rear side in the sheet width direction leading contacts the rear paper width sensor contact portion 52R and the front end portion of the sheet on the front side in the sheet width direction does not contact the front paper width sensor contact portion 52F, the paper width sensor 52 rotates by the force with which the sheet is conveyed. Then, the rotation state is detected by the paper width sensor detection unit 53. Thereby, in the present embodiment, the T value in the obliquely advancing state becomes smaller than the T value in the non-obliquely advancing state, which is the same as in the first embodiment. In the present embodiment, as the second timing detection means, an index value is calculated by this configuration. The algorithm for determining a side regulation setting error is also the same as in the first embodiment.

[0037] As described above, also in the present embodiment, it is possible to surely determine a side regulation setting error in the LBP apparatus main body 100 using the index value. And in the present embodiment, since the position of the registration shutter 32 unit can be arbitrarily set, such as being arranged upstream in the conveyance direction of the paper width sensor 52 unit, the degree of freedom in design is also increased. This is because, as described in the first embodiment, in the case of large skew, it is difficult to correct the skew by the registration shutter 32. For example, in the present embodiment, assume that the conveyance sensor 41 unit, the registration shutter 32 unit, and the paper width sensor 52 unit are arranged in this order from the upstream side in the conveyance direction, and the registration shutter 32 unit that plays a role in skew correction is arranged upstream of the paper width sensor 52 unit. Then, in the state where the conveyed sheet is greatly skewed, the skew is not corrected by the registration shutter 32 unit, so it becomes possible to detect the skew of the sheet by the paper width sensor 52 unit.

[0038] <Example 3> This embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a schematic perspective view of the sheet conveyance unit according to Embodiment 3, and FIG. 8 is an operation diagram of the paper width link sensor 74 unit according to Embodiment 3. 72 is the rear of the paper width flag, 73 is the front of the paper width flag, 74 is the paper width link sensor, and these three are configured to operate in conjunction with each other. The paper width link sensor 74 has a downstream sensor light-shielding portion X. Regarding the parts that overlap with the description of the above embodiments, the same reference numerals are given and the description is omitted.

[0039] As shown in FIGS. 7 and 8, in this embodiment, the rear paper width flag 72, the front paper width flag 73, and the paper width link sensor 74 are used instead of the registration shutter 32 used in Embodiment 1. In FIG. 7, the operation of the conveyance sensor 79 upstream of the front paper width flag 73, the rear paper width flag 72, and the paper width link sensor 74 functions as the first timing detection means and is the same as the function of the conveyance sensor 41 in Embodiment 1, so the description is omitted. First, the operations of the rear paper width flag 72, the front paper width flag 73, and the paper width link sensor 74 will be described with reference to FIG. 8. FIG. 8(a) shows the home position states (states where the sheet is not being conveyed) of the rear paper width flag 72, the front paper width flag 73, and the paper width link sensor 74 respectively. The rear paper width flag 72 is biased in the clockwise direction by the rear paper width flag biasing member 76, the front paper width flag 73 is biased in the clockwise direction by the front paper width flag biasing member 77, and the paper width link sensor 74 is biased in the counterclockwise direction by the paper width link sensor biasing member 78 and held in that position. Note that the biasing force of the paper width link sensor biasing member 78 that biases in the counterclockwise direction is set to be smaller than the biasing forces of the rear paper width flag biasing member 76 and the front paper width flag biasing member 77 that bias in the clockwise direction.

[0040] Here, for example, a large-slanting sheet with the back side in the sheet width direction leading is conveyed. When the leading edge of the leading sheet abuts against and passes through the rear paper width flag 72, the rear paper width flag 72 assumes the state shown in Fig. 8(b). At this point, the front paper width flag 73 is not in contact with the leading edge of the sheet on the delayed side. The contact portion α between the rear paper width flag 72 and the paper width link sensor 74 separates, while the contact portion β between the front paper width flag 73 and the paper width link sensor 74 remains in contact. Since the biasing force of the paper width link sensor biasing member 78 is smaller than the biasing force of the front paper width flag biasing member 77, the position of the paper width link sensor 74 remains unchanged from the state shown in (a). Subsequently, as the large-slanting sheet is further conveyed and the leading edge of the sheet on the delayed side abuts against the front paper width flag 73, the front paper width flag 73 assumes the state shown in Fig. 8(c). At the same time, since the paper width link sensor 74 also operates following the contact portion β of the front paper width flag 73, it assumes the state shown in Fig. 8(c). As shown in Fig. 8(c), only when both the rear paper width flag 72 and the front paper width flag 73 fall, the downstream sensor light-shielding portion X of the paper width link sensor 74 moves to make the paper width link sensor detection portion 75 transmit light, detecting the rotation state of the paper width link sensor 74.

[0041] Therefore, different from Embodiment 1 and Embodiment 2, in this embodiment, when it is largely slanting, the T value becomes larger compared to the T value when it is not slanting. Therefore, the reference data described in Embodiment 1 needs to be changed to the MIN value instead of the MAX value of the T value. Since the reference data is changed to the MIN value, the index value described in Embodiment 1 may become a negative value when not squared. Therefore, in this embodiment, the following formula is used for the index value, but the basic algorithm for determining the side regulation setting error is the same as that in Embodiment 1. TIFF0007693340000003.tif34170 As described above, even in the configuration where the sensors shown in this embodiment are linked, it is possible to surely determine the side regulation setting error within the LBP apparatus main body 100 using the index value.

[0042] <Embodiment 4> A fourth embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. 10. FIG. 10 is a flowchart showing the main flow until notification of a side regulation set error in the present embodiment. Regarding the parts overlapping with the description of the above-described embodiments, the same reference numerals are given and the description is omitted.

[0043] In the first embodiment, the side regulation set error determination as shown in FIG. 9 was analyzed in the LBP apparatus main body 100. However, in the present embodiment, it is characterized in that it is connected to an analysis apparatus 501 outside the LBP apparatus main body 100 and the analysis is performed by the analysis apparatus 501. As shown in FIG. 10, the present embodiment is composed of control in the image forming apparatus 500 in the LBP apparatus main body 100, an analysis apparatus 501 outside the LBP apparatus main body 100, and an administrative office 502. As shown in FIG. 10, the data accumulated in the image forming apparatus 500 is transmitted from a communication unit (not shown) in the LBP apparatus main body 100 to the analysis apparatus 501 outside the LBP apparatus main body 100. In the analysis apparatus 501, the transmitted data is received by a communication unit (not shown) in the analysis apparatus 501, and analysis is performed according to the algorithm shown in FIG. 10. The analysis apparatus 501 is equipped with a CPU having higher performance and a larger-capacity memory than the CPU in the LBP apparatus main body 100, enabling analysis of larger-scale data. Therefore, when the number of sheets of paper passing through increases and the number of data to be handled increases, the processing load may become excessive for the CPU and memory in the LBP apparatus main body 100, making it difficult to analyze skew detection. Therefore, by performing the skew detection analysis with the high-performance analysis apparatus 501 described above, a large amount of data processing becomes possible.

[0044] Then, the analyzed and determined results are not only displayed on a display unit (not shown) provided in the analyzer 501, but also transmitted from a communication unit (not shown) in the analyzer 501 to the management office 502 and displayed on a display unit (not shown) provided in the management office 502. Regarding the display content, for example, the display on the analyzer 501 is the numerical value of specific index values and OK or NG determination, while the display on the management office 502 is more specific, such as "Please confirm because Side Regulation 24 may not be set correctly". As described above, in this embodiment, by performing the analysis of the detected skew data with a high-performance analyzer 501 outside the LBP apparatus main body 100, it becomes possible to handle more data.

[0045] The control block of this embodiment will be described with reference to FIG. 12. Here, only the parts related to this embodiment are extracted and described. Inside the image forming apparatus 500, the signals of the first timing detection means 511 in the sheet conveyance path 510 and the second timing detection means 513 by the contact member 512 are input to the time difference acquisition unit 516 in the control unit 520. Then, the signal from the time difference acquisition unit 516 is input to the arithmetic processing unit 534 in the analyzer 501 connected to the image forming apparatus 500. In the arithmetic processing unit 534, the above-described arithmetic processing is performed. When the skew of the sheet is detected based on the result of the arithmetic processing, a signal is input to the management office 502, and the management office 502 notifies the skew. Further, the analyzer 501 has a CPU 531, a RAM 532, and a ROM 533 that are more high-performance than the image forming apparatus 500, enabling a large amount of data processing.

Explanation of Signs

[0046] 30: Registration roller, 32: Registration shutter, 37: Lower conveyance guide, 38: Upper conveyance guide, 39: Conveyance roller, 40: Conveyance roller, 41: Conveyance sensor, 42: Conveyance sensor detection unit, S: Sheet, A, B, C: Rotation centers, X: Downstream sensor light shielding part, Y: Upstream sensor light shielding part

Claims

1. A conveyance path for conveying a sheet, including a first moving part that moves in contact with the central part of the sheet in the width direction intersecting the sheet conveyance direction, the first moving part moving when the sheet passes through a first position in the conveyance path, and first timing detection means for detecting the first timing at which the first moving part has moved; A contact part that contacts a sheet passing through a second position downstream of the first position in the conveyance direction of the sheet in the conveyance path, the contact part having at least a first contact part capable of contacting one end side of the sheet in the width direction and a second contact part capable of contacting the other end side of the sheet in the width direction, and a second moving part configured to move from a non-detection position to a detection position when the sheet contacts at least one of the first contact part and the second contact part; Second timing detection means for detecting the second timing at which the second moving part has moved to the detection position; Skew detection means for detecting skew of the sheet based on the time difference between the first timing and the second timing; An image forming apparatus comprising the above.

2. The first contact part is provided so as to be capable of contacting a region closer to the one end than the central part of the sheet in the width direction, The image forming apparatus according to claim 1, wherein the second contact part is provided so as to be capable of contacting a region closer to the other end than the central part of the sheet in the width direction.

3. The image forming apparatus according to claim 1 or 2, wherein the first timing detection means detects, as the first timing, the timing at which a portion where the first contact part and the second contact part do not contact on the sheet passes through the first position.

4. The image forming apparatus according to any one of claims 1 to 3, wherein the first contact part and the second contact part have a function of correcting skew of the sheet when contacting the sheet. Device.

5. A conveyance path for conveying a sheet, including a first moving part that moves in contact with the central part of the sheet in the width direction intersecting the sheet conveyance direction, the first moving part moving when the sheet passes through a first position in the conveyance path, and first timing detection means for detecting the first timing when the first moving part has moved; A contact part that contacts a sheet passing through a second position downstream of the first position in the sheet conveyance direction in the conveyance path, the contact part having a first contact part that can contact one end side in the width direction of the sheet and a second contact part that can contact the other end side in the width direction of the sheet, and a second moving part configured to move from a non-detection position to a detection position when the sheet contacts both the first contact part and the second contact part; Second timing detection means for detecting the second timing when the second moving part has moved to the detection position; Skew detection means for detecting skew of the sheet based on the time difference between the first timing and the second timing; An image forming apparatus characterized by comprising the above.

6. The first contact part is provided so as to be able to contact a region closer to the one end than the central part in the width direction of the sheet, The image forming apparatus according to claim 5, wherein the second contact part is provided so as to be able to contact a region closer to the other end than the central part in the width direction of the sheet.

7. The first timing detection means detects, as the first timing, the timing when a portion where the first contact part and the second contact part do not contact on the sheet passes through the first position, in the image forming apparatus according to claim 5 or 6.

8. The first timing detection means is characterized in that the timing at which the central portion of the sheet in the width direction passes through the first position is detected as the first timing, in the image forming apparatus according to any one of claims 5 to 7.

9. The skew detection means is characterized in that when the value of the time difference is different from the value in a state where the sheet is not skewed, it is detected that skew has occurred in the sheet, in the image forming apparatus according to any one of claims 1 to 8.

10. The apparatus further includes a sheet storage unit that stores a plurality of sheets to be conveyed through the conveyance path, The skew detection means, acquires the value of the time difference for each of the plurality of sheets conveyed from the sheet storage unit, acquires, as a comparison value, the value of the time difference having the lowest degree of skew of the sheet from among the values of the plurality of time differences, acquires the difference between the comparison value and the values other than the value of the lowest time difference among the values of the plurality of time differences, respectively, compares the integrated value of the plurality of differences with a predetermined threshold value as a value indicating the degree of skew of the sheets stored in the sheet storage unit, and when the value exceeds the predetermined threshold value, determines that the sheets stored in the sheet storage unit are skewed, in the image forming apparatus according to any one of claims 1 to 9.

11. A storage unit that stores a plurality of the sheets, and a side regulation unit that regulates the sheets stored in the storage unit in the width direction, and further includes, characterized in that information regarding that the position of the side regulation unit is different from a predetermined position is notified based on the detection result of the skew detection means, in the image forming apparatus according to any one of claims 1 to 10.

12. A storage unit that stores a plurality of the sheets, and a side regulation unit that regulates the sheets stored in the storage unit in the width direction, and further includes, Data for the notification device to notify information regarding that the position of the side regulation unit is different from a predetermined position based on the detection result of the oblique detection means is transmitted, and the image forming apparatus according to any one of claims 1 to 10 is characterized by this.

13. The first timing detection means includes a first sensor that detects the movement of the first moving unit, The second timing detection means includes a second sensor that detects the movement of the second moving unit, and the image forming apparatus according to any one of claims 1 to 12 is characterized by this.

14. Regarding the sheet conveyance direction, the image forming apparatus according to any one of claims 1 to 13 is characterized in that the position of the second moving unit and the position of the first moving unit do not overlap.

Images